When an alkaline battery is stored for a long period of time, zinc serving as the negative electrode active material is corroded by the electrolyte, and hydrogen gas is produced inside the battery. Consequently, the hydrogen gas increases the pressure in the battery, thereby creating a risk of electrolyte leakage. To address this problem, a zinc alloy containing a metal (an inhibitor) such as indium is generally used as the negative electrode active material.
Another known phenomenon which degrades the storage characteristics is as follows. In an alkaline battery stored for a long period of time, iron which is a base material of the battery can is corroded. Consequently, internal resistance of the battery increases, and discharge performance disadvantageously decreases. Patent document 1 describes, as a measure to address this problem, a technique to add an additive such as a titanium-containing oxide to a positive electrode. According to this technique, before iron begins to corrode, an oxidation-reduction reaction occurs between the iron and the additive, and consequently, the reaction product is deposited on the inner surface of the battery can, thereby reducing corrosion of the inner surface of the battery can.
Meanwhile, it is known that a titanium-containing oxide added to a positive electrode is effective not only in preventing rust, but also in alleviating reduction of discharge performance.
For example, it is considered that anatase titanium dioxide is effective in increasing mobility of ions when a battery is discharging. Patent Document 2 describes that addition of anatase titanium dioxide to a positive electrode inhibits polarization occurring in discharge of a battery, and consequently, reduction of discharge performance can be alleviated.
It is also considered that Ti(OH)4 or TiO(OH)2 effectively assists a positive electrode active material in retaining an electrolyte. Patent Document 3 describes that addition of Ti(OH)4 or TiO(OH)2 to a positive electrode inhibits an increase in internal resistance caused by electrolyte exhaustion at the end of discharge, and accordingly, a voltage drop occurring at the end of discharge can be alleviated.